Evidence of Fermi acceleration of Lyα in the radio galaxy 1243+036

The high-redshift radio galaxy 1243+036 (z = 36)presents an asymmetric Ly alpha profile of FWHM 1550 km s(-1) as measured by van Ojik et al. We propose that the blue asymmetry in the Ly alpha profile is not due to narrow absorption dips but consists of narrow emission peaks. We interpret the blueshifted peaks near -1130, -850, and -550 km s(-1) (relative to the peak of full profile) as being the result of Fermi acceleration of Ly alpha produced by jet-induced star formation in the wake of a 300 km s(-1) shock. This shock would be caused by the deflection of the radio jet at the observed position of the radio bend which also coincides spatially with the excess Ly alpha emission reported by van Ojik et al.